88 Parasitic Arthropods 



The peculiar disagreeable odor of the adtdt bed-bug is due to the 

 secretion of the stink glands which lie on the inner surface of the 

 mesostemum and open by a pair of orifices in front of the metacoxse, 

 near the middle line. In the nymphs, the thoracic glands are not 

 developed but in the abdomen there are to be foimd three unpaired 

 dorsal stink glands, which persist until the fifth molt, when they 

 become atrophied and replaced by the thoracic glands. The nymphal 

 glands occupy the median dorsal portion of the abdomen, opening 

 by paired pores at the anterior margin of the fourth, fifth and sixth 

 segments. The secretion is a clear, oily, volatile fluid, strongly acid 

 in reaction. Similar glands are to be found in most of the Hemiptera- 

 Heteroptera and their secretion is doubtless protective, through 

 being disagreeable to the birds. In the bed-bug, as Marlatt points 

 out, "it is probably an illustration of a very common phenomenon 

 among animals, i. e., the persistence of a characteristic which is no 

 longer of any special value to the possessor." In fact, its possession 

 is a distinct disadvantage to the bed-bug, as the odor frequently 

 reveals the presence of the bugs, before they are seen. 



The eggs of the bed-bug (fig. 70) are pearly white, oval in out- 

 line, about a millimeter long, and possess a small operculum or cap 

 at one end, which is pushed off when the young hatches. They are 

 laid intermittently, for a long period, in cracks and crevices of beds 

 and fiuniture, under seams of mattresses, under loose wall paper, 

 and similar places of concealment of the adult bugs. Giratilt (1905) 

 observed a well-fed female deposit one hundred and eleven eggs 

 during the sixty-one days that she was kept in captivity. She had 

 apparently deposited some of her eggs before being captured. 



The eggs hatch in six to ten days, the newly emerged nymphs 

 being about 1.5 mm. in length and of a pale yellowish white color. 

 They grow slowly, molting five times. At the last molt the mesa- 

 thoracic wing pads appear, characteristic of the adult. The total 

 length of the nymphal stage varies greatly, depending upon condi- 

 tions of food supply, temperature and possibly other factors. Mar- 

 latt (1907) found under most favorable conditions a period averaging 

 eight days between molting which, added to an equal egg period, 

 gave a total of about seven weeks from egg to adult insect. Girault 

 (19 1 2) found the postembryonic period as low as twenty-nine days 

 and as high as seventy days under apparently similar and normal 

 conditions of food supply. Under optimum and normal conditions 

 of food supply, beginning August 27, the average nymphal life was 



